If we only want to make 1000g of dough not 2063g we only have to multiply each ingredient weight by 1000 and divide by 2063 and the result is: Water = 315, Flour = 485, Sourdough = 189 and salt= 11.

I only understand the metric system and I find the calculations
above quite simple but for those who are used to imperial
and allergic to calculations all this must be a nightmare.
Don’ t worry I use a calculator to work out my ingredients
because I know that one day I will make a miscalculation and
this would ruin my baking day. This calculator works in weight,
you have to give it your HL (Hydration level) (put 65 if you don’ t know and
go +1 or -1 on the next batch until you are happy with your
dough).

The Amount of leaven per litre of water is 600 gr but
you can regulate your fermentation by adjusting this amount. For example on a hot summer day
you can use only 400 gr of leaven.

Specify the number of breads you are going to make and give one
of the following weight: - flour per bread (not including
flour used in the leaven) - leaven per bread - final
dough per bread.

To finish on this subject you can use Pounds or Ounces
if you are not familiar with grams, I have excluded cups because
I use only weight (I have one of those magic digital scales) but if
I find that my calculator is not helping a large number of people I will modify it accordingly, try The ingredient calculator you can also try The volumes calculator as it may help you too.